1. Field of the Invention
The present invention relates to a management system for maintaining and managing a permanent connection in an exchange network which is composed of a plurality of nodes connected mutually through a transmission path.
2. Description of the Prior Art
For instance, in a exchange network like a frame relay, a service of PVC (Permanent Virtual Circuit) in which a virtual path is set up by registering parties of communication in the exchange network previously so that transmission path can be used as though it were a common carrier leased line has been executed. The exchange network has assigned all of the nodes through which the virtual path by one PVC passes, and has made the assigned nodes register a discrimination information of the PVC and a discrimination information of input/output channels in the node for the PVC, so as to put the PVC service into operation. The discrimination information thus registered, so that a frame transmitted from the transmission terminal will be transferred to each node in which the PVC is set up one after another and will be transmitted to the other party of the communication without installing a center which controls each node intensively within the exchange network.
By the way, if a trouble occurs in one of the nodes in which one PVC is set up or in a transmission path, frames transmitted by the PVC will be abandoned at the trouble portion. Therefore, the communication through this will be inexecutable. However, other node in which the PVC is set up and terminals which transmit frames through the PVC are not capable of recognizing the trouble occurrence. Accordingly, the nodes and the transmission terminal will continue transmitting or transferring frames as before even after the trouble occurs. The fact will cause a loss of communication contents, and will cause a waste of exchange network resources.
For this reason, in a traditional exchange network, a management by SNMP (Simple Network Monitoring Protocol) has been executed. In the SNMP, a monitoring node which monitors a PVC state in all nodes composing the network is provided, and PVC state monitoring informations from each node are accumulated into the monitoring node. The monitoring node executes an intensive monitoring of the PVC state within the network with the accumulated PVC state monitoring information, and executes such controls as making the PVC invalid as occasion demands. An outline of the intensive monitoring in the traditional exchange network will be described on the basis of FIG. 14.
In FIG. 14, each node 21 detects whether or not a link (a transmission path, an interface) L between the node 21 and the adjacent nodes 21 is down by mechanical means, and holds the detected information (a state notifying information). Hereupon, the down of the link means that the transferring of the frame becomes inexecutable due to the disconnection of the transmission path, the trouble of the adjacent node 21 and so on. The monitoring node 20 executes a polling for all of the nodes 21-1-21-6, periodically or according to circumstances, to command them to transmit the state notifying information. Then, the monitoring node 20 receives the state notifying information that each node 21 transmitted corresponding to the command, and recognizes the down of the link by analyzing each of the received information. Besides, the monitoring node 20 distributes the information concerning the link down to all of the nodes 21, and directs the nodes 21 to do such processes as invalidating the PVC whose frame transmission would become impossible by the down of the link 21.
However, the monitoring node 20 is not connected to each of the nodes 21 directly. For this reason, the information exchanged between the monitoring node 20 and the distant nodes (21-2-21-6 in FIG. 14) which are not connected directly to the monitoring node 20 is relayed by the nodes that were existing between them. For instance, the information exchanged between the node 20 and node 21-1 is relayed by the node 21-1 and passed through the transmission path L1 and L2. Besides, the information exchanged between the node 20 and the node 21-3 is relayed by the node 21-1 and passed through the transmission paths L1, L2 and L7. Accordingly, the capacity of the transmission paths has been occupied to a large extent, since the information concerning the plurality of nodes were transmitted simultaneously in the transmission paths L1 and L2. As mentioned hereinbefore, the transmission path has not been used effectively in the traditional intensive monitoring system.
Besides, in the traditional intensive monitoring system, the monitoring node 20 does not recognize the information concerning the PVC which is set up in each of the nodes 21. Thus, the monitoring node 20 could not assign the nodes to be distributed, so that it had to distribute the down information to all of the nodes, even though the information is needed only by the nodes in which the PVC passing through the downed link is set up. Accordingly, the transmission path has been given further excessive load, since the down information was also distributed to the nodes which did not need the information.